Aqueous lubricant compositions containing alkanolamine salts of carboxylic acids

ABSTRACT

LUBRICANT COMPOSITIONS ARE PROVIDED CONTAINING, AS A METAL ANTI-STAINING AGENT, A SALT OF AN ALKANOLAMINE AND A CARBOXYLIC ACID HAVING AT LEAST 12 CARBON ATOMS PER MOLECULE, AND, AS A STABILITY IMPROVER, A SALT OF AN ALKANOLAMINE AND A CARBOXYLIC ACID HAVING FROM ABOUT 6 TO 11 CARBON ATOMS PER MOLECULE. THESE COMPOSITIONS ARE PARTICULARLY EFFECTIVE AS CUTTING FLUIDS IN METAL MACHINING OPERATIONS.

machining operations.

United States Patent A'Bsmlic'r or THE DISCLOSURE Lubricant compositions are provided containing, as a metalanti-stainingagent, a salt of an alkanolamine and aicarboxylic acid having at least 12 carbon atoms per [1101601116,1 and, as a. stability "improver, a salt of an alkanolamine and a carboxylic acid having from about 6 to 11 carbon atoms per molecule. These compositions: are particularly effective as cutting fluids in metal 'TBA CKGROUND OF- THE INVENTION 1 i; H 1 Field of the invention This invention relates to lubricant compositions. More par'ticularly, the invention relates to aqueous compositions adapted for use as lubricants and coolants in metal machining operations.

(2) Description of the prior art j In machining operations of metals, such as cutting, grinding, turning, milling and the like, it is customary to flood'the tool and the work with a coolant for the purpose-of carrying ofi heat which is produced during the operation. It is also customary to employ these coolants in combination with various agents having lubricat'ingand extreme-pressure properties for reducing friction' between the tool and workpiece, particularly in operations such as tapping and broaching. In this respect, it has, heretofore, been the, practice to employ for such purposes aqueous compositions containing such lubricating agents as emulsified petroleum or non-petroleum additives. Such aqueous cuttingfiuids',in order to perform satisfactorily, should meet certain important requirements. -z1Among therequirements for a satisfactory cutting fluid are.corrosion-inhibitingproperties, particularly for the purpose of avoiding staining of non-ferrous metals such as aluminum, copper or their alloys, under conditions of op -eration. Otherimportant requirements include good' antiwear properties, long'batch life, stability and avoidance 'of excessive foam formation. Prior to the present invention, soaps of relatively 'low'molecular weight monocarboxylic acids have been employed as rust inhibitors for for aqueous metal working lubricants. These materials, however, have frequently been found to be unsatisfactory because of their inability to prevent staining, particularly in alkalinesystems, of non-ferrous metals.

The* use of alkanolamine salts of carboxylic acids for impartingcorrosion-resistance to aqueous lubricant compositions, particularly as cutting fluids in metal machining operationsfis'disclosedin my Pat. No. $374,171, issued Mar.- 19, 1968. In this respect, I have found that unless a carboxylic acid having at'le'a'st 12 carbon atoms per molecule is reacted with the alkanolamine, metal-staining, particularly of non-ferrous metals, such as aluminum, is encountered, when cutting fluids containing such salts are employed. on the other hand, I have also found that ice when the salt is produced by reaction of the alkanolamine with a carboxylic acid having at least 12 carbon atoms per molecule, although such metal-staining by the lubricant is inhibited, the lubricant, nevertheless, exhibits poor stability and separation of undesirable residues, accompanied by foaming tendencies, particularly in soft water areas, is encountered.

SUMMARY OF THE INVENTION It has now been found that aqueous lubricant compositions can be elfectively inhibited against the staining of metals while also exhibiting stability, avoidance of excessive foam formation, good anti-wear properties and relatively long-batch life, by incorporating therein a metal anti-staining agent, comprising a salt of an alkanolamine and a carboxylic acid having at least 12 carbon atoms per molecule, and, as a stability improver, a salt of an alkanolamine and a carboxylic acid having from about 6 to 11 .carbon atoms per molecule. These compositions are particularly effective as cutting fluids in metal machining operations.

The foregoing improvements, as more fully hereinafter described, are, in general, realized with aqueous lubricant compositions containing, as essential components a minor amount, of each, of the aforementioned alkanolamine salt of a carboxylic acid having at least 12 carbon atoms per molecule and the aforementioned alkanolamine salt of a carboxylic acid having from about 6 to 11 carbon atoms per molecule.

As hereinbefore indicated, each of the aforementioned alkanolamine salts is employed in minor amount, suflicient to prevent staining of metal, while at the same time maintaining stability. In most applications each of these two salts is employed in an amount from about 0.1 to about 20%, and preferably from about 1 to about 10%, by weight, of the total lubricating composition.

The acids employed for the formation of each of the desired salts, as hereinbefore indicated, comprise carboxylic acids. Thus, the acid employed for imparting antistaining properites comprises any carboxylic acid having at least 12 carbon atoms per molecule andparticularly preferred, and exemplary thereof are monomer, dimer and trimer acids, or mixtures thereof, of the type hereinafter described. The acids employed for imparting stability of the corresponding alkanolamine salt to the lubricant, as

.hereinbefore indicated, may comprise nay carboxylic acid having from about 6 to 11 carbon atoms and preferably include hexanoic, heptanoic, caprylic, pelargonic decanoic acids and para tertiary butylbenzoicacid. In this respect, it is found that the aforementioned salts of relatively low molecular weight acids, i.e. acids having from about 1 to 5 carbon atoms per molecule, do not satisfactorily function as anti-rust agents and are objectionable'because of their strong odor. On the other hand, it is found that by employing carboxylic acids having from-about 6 to 11 carbon atoms per molecule, improved hard water stability is obtained and high foaming tendency is avoided.-

In forming the stain inhibitor and stability improver any alkanolamine may be reacted with the carboxylic acid. This alkanolamine may be of any molecular weight but should, preferablybe liquid at-room temperature. The lower .molecular weight compounds are generally preferred and, f or ,this purpose, :it isfound that such alkanolployed andm ay. include such 'alkanolamines as iso-propanolamines, e.g. mono, dli'and tri-isopropanolamine, di-

methylethanolamine, diethyl-ethanolamine, aminoethylethanolamine, N acetyl ethanolamine, phenyl ethanolamine, phenyldiethanolamine and mixtures thereof. It should be noted that insofar as the salts are concerned, they may be preformed by reaction of a suitable alkanolamine with the stoichiometric amount of the selected acids, and then adding the salts thus formed to the lubricant composition. On the other hand, if so desired, the salt inhibitor may be formed in situ, by carrying out the reaction between the alkanolamine and the acids by mere admixture in the lubricant composition itself.

In combination with the aqueous base lubricant containing the above-described salts of the organic acids as stain inhibitors and stability improvers, other additive components may also be included for their added beneficial effect. These may include, for example, minor amounts of rust inhibitors, such as alkali-metal nitrites, preferably in an amount from about 0.1 to about 10% by weight; minor amounts of copper corrosion inhibitors, for example, benzotriazole, preferably in an amount from about 0.1 to about 3% by weight; minor amounts of biocidal agents, preferably in an amount from about 0.1 to about 3% by weight of such biocides as boric acid and chlorinated cresols, e.g. para-chlorometa-cresol. Also, if so desired, other additional additives may be present, including minor amounts of anti-wear agents, preferably in an amount from about 0.1 to about 10% by weight, for example, copolymers of equimolar mixtures of ethylene oxide and propylene oxide. When the salts are to be prepared in situ, each of the carboxylic acids are employed in a minor amount, preferably in a total amount of from about 1 to about 50%, by weight, while the alkanolamine is preferably employed in an amount from about 5 to about 50%, by weight.

In addition to the aforementioned preferred components of the novel aqueous lubricant composition of the present invention, other representative varieties of additives may also be incorporated, in minor amounts, either as additional or substitute components. Such additives, in addition to the aforementioned copolymers of equimolar mixtures of ethylene oxide and propylene oxide, may include other water-soluble polyoxyalkylene glycols as load-support agents, including water-soluble hetero copolymeric alkylene glycol ethers or esters thereof, wherein the different oxyalkylene units are substantially randomly distributed throughout the entire polyoxyalkylene chain; water-soluble polyoxyalkylene compounds containing hydrophobic homopolyoxyalkylene units and polymeric agents, in general, which are block copolymers of conjugated polyoxyalkylene compounds containing at least one hydrophobic homopolyoxyalkylene unit, having a unit weight of at least about 800, and one or two other hydrophilic polymeric units which comprise from about 15% to about 90% of the total polymeric compound.

In addition to the aforementioned preferred biocidal agents, other biocidal materials may be employed in the novel formulation and may include para-bromo-metacresol; para-fluoro-meta-cresol; para-iodo-meta-cresol; 2,4- dichloro-meta-cresol; 2,4,S-trichloro-mta-cresol; 2,4,5,6- tetrachloro-rneta-cresol; 2,4 dibromo-meta-cresol; 2,4,5- tribromo-meta-cresol; 2,4,5,6-tetrabromo-meta-cresol; or any of the aforementioned compounds in which the chlorine or bromine atoms are substituted in whole or in part by fluorine or iodine; or any corresponding ortho or paracresols of the aforementioned compounds substituted for the corresponding meta-cresols.

Still other biocidal agents that may be employed in the above-described novel formulations may include microbiocidal gases, for example, in the form of aldehydes, such as formaldehyde, or aldehyde-releasing agents, such as formaldehyde-releasing agents, i.e. materials which break down in storage to form the aldehyde or aldehyde compounds as decomposition products. Thus, it is found that compounds of the type such as tris(hydroxymethyl) nitrornethane are particularly effective in releasing formaldehyde and thereby providing biocidal protection ,over relatively long periods of time. Other microbiocidal gases that may be employed for this purpose include ethylene oxide and beta propiolactone. Alcohols such as methyl alcohol, ethyl alcohol or higher alcohols may also be employed as biocidal agents. Other effective biocidal agents include halogens and halogen compounds, particularly iodine and chlorine and compounds of these halogens. Specific compounds of this type may include chloride of lime and iodophors. Furthermore, as biocidal agents, compounds of heavy metals may also be employed in the novel formulations. These may include such compounds as bichloride of mercury and organic mecurials such as mercurochrome, merthiolate, metaphen, silver nitrate and copper sulfate. Biocidal agents comprising phenol and its derivatives may also be employed in the novel formulations, which include the aforementioned cresols and hisphenols. Synthetic detergents may. also be employed as biocidal agents, which are the non-phenolic type. These may include, for example, ammonium halides, such as ammonium chloride, in which the hydrogen atoms have been replaced by organic radicals; particularly effective are quaternary compounds in which the long-chain organic radical (alkyl group) contains from 12 to 16 carbon atoms. Other materials include quaternary compounds in which the organic group is an anion, e.g-., sodium laurylsulfate, as well as those compounds which do not ionize.

The novel lubricant compositions of the present invention are preferably prepared by a blending procedure which comprises reacting the salt-forming components, i.e. alkanolamine and organic acid components with about 10 to about 20 parts of water, which is to be present in the finished formulation. This blending procedure may be carried out at room temperature. However, heating to 160 F. with agitation is most satisfactory. The remaining quantity of water required to be present in the finished formulation is added together with any of the aforementioned other desired components. It should be noted, however, that if an alkali-metal nitrite is to be present in the finished product, such material should be added last, for the reason that addition of acids, such as caprylicacid, to a solution of sodium nitrite, could result in decomposition of the nitrite, thereby reducing or nullifying its rustinhibiting effects. If a biocidal agent is to be incorporated in the novel formulation, it is preferably blended with the alkanolamine and organic acids employed.

DESCRIPTION OF SPECIFIC EMBODIMENTS I,

The following examples, comparative data and observations will serve to illustrate the novel lubricant compositions of the presentinvention and the improved metal stain-inhibiting and stabilizing properties realized because of the presence of the aforementioned alkanolamine salts of organic acids. -In each of the comparative examples, the aluminum stainrtest employed comprised placing approximately /2 oz. of the lubricating solution to be evaluated in a 2 oz. jar, together with a 2"/ A" rod of aluminum, previously cleaned with a medium grade of emery cloth. Approximately one half of this rod was immersed below the surface of the test solution, and the remaining portion was exposed to air. Staining tendency was observed over a period of 24 hours. In each case, the ethanolamine, acid and biocide together with from about 20 to about 30 parts of water, by weight, .were blended at a temperature of F. The remainingportion of the water and other components were then-added and this base formula was then diluted in a ratioof 1 to 40 parts with distilled water prior to running the stain tests. The copolymer employed comprised a copolymer of a 50-50 mixture of ethylene oxide. and propylene oxide. The polymer acid employed compriseda commercially available organic acid in the form of a mixture of monomer, dimer and trimer acids, commercially identified as Emery 3348 Organic Acid manufactured by Emery Industries, Inc. containing, by weight, 40% monomer,

5 47% dimer and 11% trimer acids, and having the following properties;

Color, Gardner 195a 9 AOCS Kris-5s l Neutralization equivalent is numerically equal to 56,100 divided by acid number.

- 2 Saponification equivalent is numerically equal to 56,100 divided by saponifieatlon value.

The stability test comprised a visual observation determinative of separation of lubricant components of the fluid composition undergoing evaluation. I

The base lubricant fluid employed in the comparative examples of the following table comprised, by weight: 26% triethanolamine; 4% monoethanolamine; 1.5% pchloro-m-cresol; 3% boric acid; 0.25% benzotriazole; 5% of a copolymer of an equimolar mixture of ethylene oxide and propylene oxide; 3% sodium nitrite and 50.25% water. As shown in the table, varying carboxylic acids, either individually or in combination, were added, in a total amount of 7%, to the above-described base lubri: cant and the resulting blends were evaluated for the above-described staining effect and stability characteristics. In the stain test, a rating of 1 is considered satisfactory, indicative of little or no staining, while ratings above 1 are considered unsatisfactory in increasing degree as the numerical rate rises. In the stability test, a separation of lubricant components, in the form of a residue, is considered unsatisfactory.

Aluminum Organic acid added to stain test Stability test, Example blend [wt. percent] rating 24 hrs.

1 Oleic (011;)[7] 1 Separation; 2 gapryliic gagglun 3 No separation,

apry c a 3 "igecanfiic 3 apry c 4 -.{g u g M51 1 Do.

apry c a 5 uhg l ($1 1 1 Do apry 1c 2 6 -{8 g gg im 1 Do.

a ry e a 7 "{Emery 334s (0:0)[4 1 8 Emery 3348 (Cao)[7] 1 Separation.

Para-tertiary butyl benzoic 9 acid( [3. 1 No separation.

Emery 3848 (Cao)[4] 10 Para-tertiary butyl benzoie 3 Do.

acid (On)[7].

As will be seen from the foregoing table, in Examples 1 and 2, the presence of oleicacid alone (for forming the corresponding alkanolamine salt) provides a satisfactory stain test result, but also results in poor stability of the lubricant with separation taking place. The presence of caprylic acid alone, provides satisfactory stability, but results in unsatisfactory staining. In Example 3, it will be noted that the combination of two carboxylic acids each having less than 12 carbon atoms per molecule, results in a lubricant having good stability but unsatisfactory staining. On the other hand, as shown in Examples 4, 5, 6 and 7, where a combination of two acids is employed, one acid having less than 12 carbon atoms and the other having 12 or more carbon atoms per molecule, satisfactory stability and stain tests results are achieved.

It will also be noted that in Example 8 the presence of the Emery 3348 acid alone (for forming the corresponding alkanolamine salt) provides a satisfactory stain test result, but also results in poor stability of the lubricant with separation taking place. In Example 10, the presence of the para-tertiary butyl benzoic acid alone results in a lubricant having good stability, but unsatisfactory staining. On the other hand, as shown in Example 9, where a combination of the two acids is employed, satisfactory stability and stain test results are achieved.

While preferred embodiments of the compositions of the present invention have been described for purposes of illustration, it will be understood that various modifications and adaptations thereof, which will be obvious to those skilled in the art, may be made without departing from the spirit of the invention.

I claim:

1. An aqueous lubricant composition containing, in minor amounts, as a metal anti-staining agent, a salt of an alkanolamine and a hydrocarbon carboxylic acid containing at least 12 carbon atoms per molecule, and as a stability improver, a salt of an alkanolamine and carboxylic acid selected from the group consisting of hexanoic, heptanoic, caprylic, pelargonic decanoic acids and para tertiary butylbenzoic acid.

2. A lubricant composition as defined in claim 1 wherein each of said salts is present in an amount from about 0.1 to about 20%, by 'weight.

3. A lubricant composition as defined in claim 1 wherein each of said salts is present in an amount from about 1 to about 10%, by weight.

4. A lubricant composition as defined in claim 1 containing, as an'additional component, from about 0.1 to about 10%, by weight, of awater-soluble copolymer of ethylene oxide and propylene oxide.

5. A lubricant composition as defined in claim 1 containing, as an additional component, from about 0.1 to about 3%, by weight, of an alkali metal hyroxide.

6. A lubricant composition as defined in claim 1 containing, as an additional component, from about 0.1 to about 3%, by weight, of a biocide comprising boric acid.

7. A lubricant composition as defined in claim 1 containing, as an additional component, from about 0.1 to about 3%, by weight, of a biocide comprising a chlorinated cresol.

8. A lubricant composition as defined in claim 1 containing, by weight: from about 0.1 to about 20% each of alkanolamine salts of (a) a mixture of monomer, dimer and trimer acids having an acid number of 184- 190, and alkanolamine salts of b) caprylic acid and wherein the alkanolamine is selected from the group consisting of monoethanolamine and triethanolamine and mixtures thereof; from about 0.1 to about 10% of sodium nitrite; from about 0.1 to about 10% of a copolymer of ethylene oxide and propylene oxide; from about 0.1 to about 3% of benzotriazole; from about 0.1 to about 3% of boric acid; from about 0.1 to about 3% of parachloro-rneta-cresol; and the balance water.

9. A lubricant composition as defined in claim 1 containing, as additional components, from about 0.1 to about 10% by weight, of an alkali-metal nitrite and from about 0.1 to about 3%, by weight, of benzotriazole;

10. A lubricant composition as defined in claim 1 containing, as additional components, from about 0.1 to

(References on following page) References Cited UNITED STATES PATENTS Davis 25234.7

Saunders 25234.7

Plemich 25234.7

Schiermeier et al. 25234 Teeter et a1. 25234.7

5/1966 Great Britain 25 DANIEL E. WYMAN, Primary Examiner A. H. METZ, Assistant-Examiner Po-mso UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. $769 O I Dltld October 30, 973 Immfl") R BERT H DAVIS. I

It is cartifiod that error appears in the above-identified patent and that aid Ll ttll'l Patent arehcreby corroctod as shown below:

Column 6, line 26, aft er a.nd" insert -a--.

Signed and sealed this 5th day of March 197L (VS-EAL) Attesc: I \V EDWARD Mj'LETcHEm-JR, 1. MQtRS HA LL DANN': Attesting Officer Commlssi of Patents 

